1. Field of the Invention
This invention relates to electromagnetic switching devices and particularly to an improved magnetic latching reed relay.
2. Description of the Prior Art
One type of a magnetic latching read relay includes a pair of reeds made from a magnetic material which, when exposed to a magnetic flux, will assume a magnetic state and remain in that state until exposed to a magnetic flux of opposite direction. The ends of the reeds overlap to function as a pair of normally open contacts. An example of such a relay is taught by U.S. Pat. No. 3,059,075 issued to R. L. Peek on Oct. 16, 1962.
Various arrangements of control windings have been employed with magnetically latched reed relays. One such arrangement is taught by U.S. Pat. No. 3,037,085 issued to T. N. Lowry on May 29, 1962. That arrangment employs the principle of differential excitation and employs two pairs of windings connected so that the relay is released, i.e., the contact pair is opened, by applying a current pulse to one pair of windings and the relay is operated, i.e., the contact pair is closed, by concurrently applying pulses of the same polarity to both pairs of windings.
Another control winding arrangement taught by U.S. Pat. No. 3,793,601 issued to R. J. Anger et al. on Feb. 19, 1974 operates or releases the reeds with a single pulse. Each of a pair of identical release windings is arranged over a corresponding one of a pair of reeds. The release windings are series connected so that a single pulse applied to the windings causes a magnetic field of one direction to be produced around one reed and a magnetic field of an opposite direction to be produced around the other reed. The resultant magnetic flux is such that the contact ends of the reeds are of the same magnetic polarity and thus separate. An operate winding in association with one of the two release windings is wound in a manner to produce a magnetic flux magnitude greater than the magnitude magnetic flux generated by the associated release winding and having a flux direction opposite to the flux direction produced by the associated release winding. The operate winding is series connected to the associated release winding so that a single current pulse flowing through the operate and the pair of release windings causes the contact ends of the reeds to have magnetic states of opposite polarity with the result that the contact ends of the reeds attract whereby the contact pair is closed.
The arrangement taught by the Anger patent has an inefficiency in its operation to close the reed contacts in that the operate winding must generate a magnetic field of sufficient strength to overcome the magnetic field concurrently produced by one of the release windings.